Polaronic effects on the collective excitation energies in a quantum wire

In this work we report a investigation of the plasmon–longitudinal-optical (LO) phonon interaction effects on the intersubband and intrasubband collective excitation energies in a GaAs–Al_νGa_1?νAs rectangular quantum well wire. We observe a resonant split of the collective excitation energy into two branches, one with energy lower and other with energy higher than the LO-optical phonon energy ?ω_LO. Our calculations are performed using a self-consistent field approximation, which includes the local-field correction within the Singwi, Tosi, Land, and Sjolander (STLS) theory at zero temperature and assuming a three-subband model, where only the first subband is occupied by electrons. The potential confining effects on the collective energies were also considered.     

Processing and characterization of a biaxially oriented conducting polymer

Two methods have been developed for the preparation of biaxially oriented poly(phenylene vinylene) from its poly(sulfonium salt) precursor. A two-stage stretching process permits non-equibiaxial stretching over a wide range of deformation ratios and a bubble expansion technique allows equibiaxial planar extension. The resulting films were examined using X-ray diffraction prior to chemical doping with SbF₅ vapor. Biaxial orientation was shown to exert considerable influence over the attainable electrical conductivity.     

The effect of extremely low lubricant volumes in machining

Cost, the effect on the environment, and health issues are all relevant when considering the choice of a lubricant and application system in a modern metal cutting process. The need to use less, limit the disposal and operator contact are all now very important. This paper shows the results of preliminary tests using very low quantities (200–300 ml h⁻¹) of lubricant when machining steel. The low quantities were applied in a fast flowing air stream. The results are compared to traditional flood cooling as a benchmark with 5.2I min⁻¹. The results show that surface finish, chip thickness and force variation are all affected beneficially with the low coolant volume compared to flood cooling.     

Decolorisation of real textile waste using electrochemical techniques: effect of the chloride concentration

The present paper presents the study of the decolorisation of real textile effluent by constant current electrolysis in a flow-cell using a Ti/Ru(0.3)Ti(0.7)O(2) DSA((R)) type electrode. The effect of increasing the chloride ion concentration on the efficiency of colour removal is discussed. Attempts to perform galvanostatic oxidation (40 and 60mAcm(-2)) on the as-received effluent demonstrate that colour removal and total organic carbon (TOC) removal are limited. If the conductivity of the effluent is increased by adding 0.033molL(-1) Na(2)SO(4), little increase in the extent of colour/TOC removal is observed. However, when Na(2)SO(4) is substituted, stepwise, with NaCl (while maintaining the ionic strength constant) appreciable colour/TOC removal is observed. The study of the effect of increasing the current density demonstrates that total colour removal is possible at high currents. The efficiencies of colour and TOC removal are discussed in terms of the Energy per order (E(EO)/kWhm(-3)order(-1)) and Energy consumption (E(C)/kWhkg(-1)TOC), respectively. Finally, the extent of colour removal is compared to consent levels presented in the literature.     

DETERMINATION OF DIACETYL IN BEER USING DIFFERENTIAL-PULSE POLAROGRAPHY

A Polarographie method is proposed for the determination of diacetyl and other vicinal diketones in beer. Similar to the EBC official spectrophotometric method, diacetyl is derivatised with o-phenylene-diamine, producing 2,3-dlmethylquinoxaline, a polarographically active compound . The Polarographic method allows discrimination between diacetyl and methylglyoxal and a detection limit ten times lower than the EBC method is obtained. In addition, problems of erratic results for diacetyl may be avoided and data are in good agreement with those obtained by gas chromatography with electron capture detection and headspace sampling . It is suggested that high results obtained with the spectrophotometric method may be attributed to an erroneous procedure used in the spectrophotometric calculations. An alternative procedure is proposed, with which lower values for diacetyl in beer are obtained, similar to those found with other methods. These low diacetyl values are near the detection limit of the spectrophotometric method .     

Development of Active Films From Pectin and Fruit Extracts: Light Protection,Antioxidant Capacity,and Compounds Stability

Pectin films containing fruit extracts were developed and tested in relation to ultraviolet light transmission, phytochemical contents, and antioxidant capacity during 90 d shelf life storage. Aqueous and alcoholic extracts from 5 different fruits (acerola, cashew apple, papaya, pequi, and strawberry) were obtained. Because the alcoholic extracts from acerola, cashew apple, and strawberry presented the highest phytochemical content and antioxidant capacity, they were incorporated into pectin films individually or as a mixture. Incorporation of these extracts into pectin films provided antioxidant capacity while retaining the physical properties. The pectin films containing fruit extract acted as adequate light barrier and prevented photooxidation. Among the prepared films, the pectin film containing acerola extract afforded the highest antioxidant capacity, with a half‐life of 99 d. Overall, the results revealed that incorporation of fruit extracts into pectin films potentially produces antioxidant films and coatings for different food applications.     

Sensory acceptability of raw and extruded bovine rumen protein in processed meat products

The use of bovine rumen protein (raw and extruded) as a replacement for extruded soy protein concentrate in three meat products (pork sausage, chicken hamburger, and kibbe) was investigated. Similarity between rumen and soy protein meat products was assessed using triangle tests and sensory acceptability evaluated by consumer panelists using a nine-point hedonic scale. The addition of raw rumen protein was detected in all meat product types tested, while extruded rumen protein was only detected in kibbe. The addition of raw rumen protein decreased the acceptability of pork sausage aroma and flavor, but improved kibbe appearance, texture and overall acceptability. The addition of extruded rumen protein reduced the acceptability of chicken hamburger texture, but improved pork sausage flavor. Replacement of soy protein by bovine rumen protein is feasible based upon sensory results, but depended upon its form and the type of meat product to which it was added.     

Preparation and characterization of ethylene‐vinyl acetate nanocomposites: enhanced flame retardant

Ethylene‐vinyl acetate (EVA) nanocomposites with enhanced flame retardance were prepared by the sol–gel process in the melt. Two EVAs with different vinyl acetate (VA) contents and aluminium isopropoxide were used as organic and inorganic phases. The nanocomposites were prepared in a batch mixer under constant processing conditions and were analysed by several characterization techniques. Aluminium isopropoxide presented low activation energy, which allows the synthesis of the nanoparticles without a post step treatment. The reaction mechanism is proposed. Nanocomposites with smaller and well dispersed metal nanoparticles were produced with an EVA with higher VA content. EVA nanocomposites achieve the requirements for 94 V‐0 classification. © 2013 Society of Chemical Industry     

Chromogenic anionic chemosensors based on protonated merocyanine solvatochromic dyes: Influence of the medium on the quantitative and naked-eye selective detection of anionic species

Three merocyanine solvatochromic dyes, Brooker's merocyanine, Reichardt's dye and 4-(2,4,6-triphenylpyridinium-1-yl)phenolate were solubilized in acetonitrile. Although solutions of each of the compounds are colored, the color disappears after protonation. Addition of various anions to solutions of the protonated dyes revealed that only CN^?, F^?, and H₂PO₄^? led to the reappearance of the original color of protonated Reichardt's dye, and only CN^? and F^? ions caused the original color of the solutions containing the other two protonated dyes to reappear. Addition of small amounts of water to solutions containing the protonated compounds made them useful only for detecting CN^? among all the other anions. A model was used to explain the experimental results, which considers proton transfer from the protonated dye to the anion through three dye:anion stoichiometries, namely 1:1, 1:2, and 1:3.     

Boron and nitrogen functionalized diamondoids: A first principles investigation

Chemically functionalized adamantane molecules have been investigated by first principles total energy calculations. Boron and nitrogen functionalized molecules were found to be very stable, consistent with available experimental data. Two hypothetical molecular crystals, involving functionalized adamantane, were investigated. These molecular crystals presented direct electronic bandgaps and large bulk moduli, which suggested a possible road for molecular self-assembly using functionalized diamondoids.